Metal Roof with Cathedral Ceiling above Rafters (exposed beams)

ICANZ System Reference R0500

Structure

Tiled cathedral roof at 22.5o pitch, with foil draped under tile batten providing 40mm air space with bright side of foil facing downward. Tile battens fixed over counter batten providing minimum 70mm airspace. 10mm plasterboard ceiling fixed under counter batten but over exposed roof rafter.

Insulation Installation

Option 1: Single sided polyweave foil positioned over batten. Reflective polystyrene positioned at mid height of original 70mm air space providing 20mm air space above and below reflective EPS board.

Option 2: Single sided polyweave foil positioned over batten. Original 70mm air space below single sided polyweave foil replaced with 20mm air space and R1.5 - 50mm bulk insulation. Bulk insulation on the ceiling lining.

NOTE: Total R-Values can be increased by substituting bulk insulation products of higher Material R-Value.

 Metal Roof with Cathedral Ceiling above Rafters (exposed beams)Metal roof cathedral ceiling above rafters

A. In accordance with AS/NZS 4859.1:2002.  Amendment 1. 2006.
B. Temperatures and parameters are based on Australian climate assumptions. Air temperature difference 12oC (36oC less 24oC) for summer conditions and 6oC difference (18oC less 12oC) for winter.
C. Thermal resistance of air films and attic spaces based on values obtained from Section K5 and K6 of AS 4859.1:2006.
D. Building material elements based on 2000 AIRAH Handbook and attic thermal value based on AS4859.1 app K6 table K2.
E. Where reflective insulation is installed, a simple addition of R-values is not possible. Care must be taken to ensure the performance of reflective air spaces is not “double-counted”.
F. The emittance of the reflective surfaces are dependent on tested values and the conditions of the installation, as specified by AS/NZS 4859.1. Amendment 1. 2006.